1. Field of the Invention
The present invention relates to an optical amplifier for amplifying signal light by pumping light and to an optical transmission system using it.
2. Related Background Art
An optical amplifier is a device for amplifying signal light transmitted through an optical transmission line, such as an optical fiber transmission line or the like, in an optical transmission system in order to compensate for transmission loss in the optical transmission line. The optical amplifier is comprised of an amplification optical waveguide, such as an amplification optical fiber or the like, and a pumping light supplying means for supplying pumping light into the amplification optical waveguide. When the signal light is injected into the amplification optical waveguide with supply of the pumping light, the input signal light is amplified in the amplification optical waveguide.
Such optical amplifiers include, for example, rare-earth-element-doped fiber amplifiers using a rare-earth element, such as Er (erbium) or the like, as a fluorescent material for the amplification. The rare-earth-element-doped fiber amplifiers (e.g., EDFA: Erbium-Doped Fiber Amplifier) are optical amplifiers using a rare-earth-element-doped optical fiber (e.g., EDF: Erbium-Doped Fiber) as an amplification optical waveguide.